They say that necessity is the mother of invention, and in this case, there's no question who the parents are!

Imagine you've got your latest and greatest project ready to go, whether that's Raspberry Pi, Arduino, or even a bunch of LED lights for your home, but you want to be able to remotely control the power to these devices.

Perhaps you're placing the project on a remote mountain top, or the project is battery powered and you want to be able to turn off devices to save power, or maybe, you're just automating that amazing home LED lighting.

You need a Power Distribution Unit!

What is it?

It's a simple concept, imagine a power strip, but for DC power, and you can control and measure the power usage of each outlet!

The DC PDU has a port for a DC supply, anywhere from 0 to 40V DC, and will supply that to 8 other individually controlled ports, up to 3A each! Each port has current and power sensing, voltage sensing on the input port, and individual control for each port!

Ready to light up the night? A simple 'PON 1' command turns on the power to Port 1! Want to see exactly how much power the device on each port is passing through? The 'STATUS' command will print a summary of all the ports, if they're on or off, how much current and power they're using, and more! Check out the GitHub page for documentation and examples for all the supported commands!

The PDU connects via a standard USB-B port on the board, and shows up on your OS X, Linux, or Windows device as a USB Serial Port. Using your favorite serial program (screen, PuTTY, minicom, etc), you can connect to the PDU, request data, and send commands!

The PDU can be powered via USB, or via a regulated 5V supply connected to the onboard 2.1mm Barrel Jack! Just flip the solder jumper on the bottom of the board from USB to Jack!

Have a need for more than 3 amps, or need to control an AC powered device? Attach a simple relay to a PDU port, and you can manage power for any device you can imagine!

Why did you make it?

I designed this device for a project I volunteer with that places network infrastructure (wireless access points and routers), at remote mountain top sites for emergency connectivity. Some of those mountain top sites are hard to reach, or a long distance away, and we needed a way to remotely reboot a router if it hung up.

There are a number of options for doing this with AC power from companies like APC or TrippLite, but very little available for DC power, which was important for our solar powered locations. Equally important was to ensure the PDU itself drew as little power as possible to avoid being a significant load on the batteries. The PDU runs from a 5V supply, and draws about 20mA. A tiny little figure, great for running off batteries.

What makes it special?

As I mentioned in the paragraph above, there are numerous options to control AC power, but they tend to draw a lot of power themselves, and at battery powered locations, you have to use an inverter to go up to mains voltage, and then another supply to regulate it back down. What a waste! Using a low power device that switches DC power directly removes the inefficiencies and makes a great option for solar or battery powered locations!

Extras!

The PDU also includes an onboard temperature sensor, to give you a clue as to the environment your projects are running in. There are six extra analog inputs that accept voltages from 0V to 4.5V and will be read out via the status commands, so you can use the PDU to help gather your data!

I've designed a 3D printable case for the PDU, and it's available in the GitHub repository for you to print yourself, print at your local hackerspace, or send to a company like Shapeways for printing!

Everyone has a different use case for a device like this, so I haven't attached connectors to the ports. You're free to solder in wires, or whatever connectors you like! I have designed them to be compatible with the wonderful Anderson PowerPole connectors with the straight PC board contacts!

FAQ

• Can the PDU run without a computer attached? Yes! The PDU ships configured to power the onboard logic via the USB port, so to start with you'll need to plug it into a computer to get it to run. Once you have it configured the way you like (default port states and voltage control parameters), you can switch the solder jumper on the bottom of the board from USB to Jack, and supply regulated 5V DC to the barrel jack (Center positive!) to supply power to the board logic. Keep in mind that the 5V for the board logic is entirely independent of the INPUT connector voltage, which has a range of 0-40V DC and gets supplied to the 8 output ports.
• What connectors can I use on the ports? I chose not to populate the connectors on the ports because everyone has different needs. You're free to solder wires or anything else you like to the ports. I did make the ports dimensions compatible with the wonderful Anderson PowerPole connectors.
• Is there a case available? Yes! I designed a case able to be 3D printed for the PDU. If you have a 3D printer, a local makerspace, or want to use a third party service like shapeways or ponoko, the OpenSCAD and STL files are available in the github repository!
• The PDU shows up on my computer as a serial device. What baud rate should I use? The PDU actually shouldn't care about baud rate. You should be able to use any rate you wish. However, for simplicity if your client program requires entering a baud rate, standard values like 9600 or 19200 work quite well.
• Can I use the PDU for inductive loads? The PDU was not designed for inductive loads, and the USB port is not isolated. For small loads you may be alright. For larger loads like motors, please consider using external clamping or a relay (with clamping on the coil) between the PDU and the motor.
• What side switching is used on the PDU? The PDU was designed to be simple and inexpensive, so Low side switching was used. This means that if your device will have an alternate path to ground, the PDU will not be able to effectively control or measure power for that device.
• Is the USB port on the PDU isolated? No. The USB port on the PDU is not isolated, and the USB ground is shared with the load ground. Please be aware of this, to ensure that any device (your computer) you connect the PDU to will not be damaged by sharing a ground with your loads.

Thanks!

Thanks for checking out my project, and I hope that it can help you wrangle the power management for your project!